Superregenerative receiver



Dec. l2, w50 T. M. FERRILL, JR., ErAL 2,533,237

SUPERREGENERATIVE RECEIVER Filed Feb. l2, 1945 lng 33 26 AF awlvcH-Fesquswv w m, Jh

7 W4 M WL? |IMIAM W 2 M 9 W4 HW w +Mw INVENTORS mo/WAS /Vl Ritek/LL., Je. A f/v E' SP5/vos@ BY A TORNEY Patented Dec.. 12, 1950 SUPERREGENERATIVE RECEIVER Thomas M. Ferrill, Jr., Hempstead, and Benjamin F. Spencer, Garden City, N. Y., assignors to The Sperry Corporation, a corporation of Delaware Application February 12, 1945, Serial No. 577,368

(Cl. Z50-20) 17 Claims.

This invention relates to wave receivers, and more particularly to receivers of the superregenerative type especially adapted for the reception of ultra-high-frequency signal waves or microwaves.

In general, a superregenerative receiver is Weil adapted for use at ultra-high frequencies. It combines inherent simplicity with high sensitivity. Its selectivity is relatively low, thus minimiz'ng the requirement for frequency stability in both the transmitter and the receiver. Furthermore, ii the logarithmic -mode of operation is employed, the oscillations always build up to an equilibrium value before quen-ching occurs, regardless of the strength ofthe input signal. A superregeneratve receiver of this type, therefore, has an inherent limiting action, so that it tends to suppress noise pulses of large amplitude but of short duration, as for example those due to automotive ignition systems.

In the past, the construction oi a superregenerative receiver for use at ultra-high frequences has had, in common with receivers of other types for use at these frequencies, the problems due to the small physical size of the reactive elements comprising the resonant circuit. As the frequency of the signal Wave becomes higher, the requirements for these components become increasingly stringent. At ultra-high frequencies, it is extremely diicult to provide circuit components which combine suitable electrical properties with a mechanical desgin capable of ma ntaining these properties in spite of variations in temperature and humidity, vibration, and other frequently unavoidable variations in the operating conditions.

Accordingly, it is an object of the present invention to provide an improved superregenerative receiver.

A further object is to provide a superregenerative receiver ci extremely compact construct'on in which the resonant circuit and the electron tube are combined in a single unit.

It is another object of the invention to provide a superregenerative receiver employing a velocitymodulation tube of the reiiex type.

It is still another object of the invention to provide a sup-erregenerative receiver employing a velocity-modulation tube which has substantial output in accordance with the received signals.

An additional object of the invention is to provide a superregeneratve receiver employing a velocity-modulation tube, in which the quenching is accomplished by varying a control voltage.

Yet another object of the invention is to provide a superregenerative recever employing a velocity-modulation tube and being of the selfquenching type.

A further object of the invention is to provide improved apparatus and instrumentalities embodying novel features and principles adapted for use in realzing the above objects and also adapted for use in other elds.

In accordance with a preferred form of the present invention, an electron tube, preferably of the reiiex velocity-modulation type having a cavity resonator, is used in combination with a rectier element to provide an improved superregenerative receiver espec'ally adapted for use at ultra-high frequencies or in the microwave region. The tube and its resonator are adjusted for oscillation at the frequency of the input signal wave, and quenching is accomplished by periodically interrupting the oscillation. In a preferred arrangement, the receiver operates in the logarithmic mode, but it may be arranged to operate in the linear mode if desired.

The invention also contemplates the provision of unitary means for introducing the input signal wave and for utilizing the output of the tube; and, in a modied form, there is contemplated an arrangement for utilizing a portion of the velocity-modulation tube to develop the quenching voltage.

The above and other objects and features of the invention will be better understood by reference to the following description taken in connection with the accompanying drawing, in which like components are designated by like reference numerals and in which:

Fig. 1 is a schematic diagram of a superregenerative receiver in accordance with the present invention and utilizing separate quenching;

Fig. 2 is a sche-matic diagram of a modification of the superregenerative receiver of Fig. l, in which self-quenching is utilized; and

Fig. 3 shows a unitary input and output system especially adapted for use with the receiver of Fig. 1.

Referring to Fig. 1 of the drawing, there is shown a reflex velocity-modulation tube l having a heater H, a cathode I2, a control electrode i3, a smoother or accelerating grid i4, a cavity resonator l5 including resonator grids 35, and a reflector electrode l5. smoother grid li is supported by and connected to cavity resonator l5. Heater ll is connected to terminals il, to which may be yconnected a suitable source of heater of filament power, not shown. Cathodey l2 is connected through resistor 2U' to a tap I8 on direct- E.: current potential source I9. Control electrode I3 is connected, through resistor 29, to a tap 2i on source I9. Cavity resonator I5 is connected by lead 22 and resistor 2li to the positive terminal of source i9, and this terminal is preferably also connected to ground, as shown at 23. Resonator grids 35 form a part of cavity resonator I5. Reflector electrode I 5 is connected through resistor 25" to a tap 2K5 on source I9.

A quench-frequency oscillator 25 is provided,

and its high-potential output terminal is coupled by means of capacitor 25 to control electrode I3 when switch G5 is closed as shown in Fig. l. The other output terminal of oscillator 25 is grounded as shown. The output of oscillator 25 preferably, but not necessarily, is sinusoidal in waveform. Similar quench-frequency oscillators 25', 25", and 25" are also provided. Oscillator 25 is adapted to have one terminal connected to the cathode I2, through a capacitor 26', upon closing of a normally open switch 55. The other output terminal of oscillator 25 is grounded. Oscillators 25 and 25 are adapted to be connected in like manner to cavity resonator I5 and redector electrode IB, respectively, upon closing oi their respective switches E5 or 65".

Cavity resonator I5 is provided with a coupling loop 2, which is connected by means of a coaxial transmission line 22 to a dipole antenna 29. A second coupling lloop in cavity resonator I5 is connected, by means of a coaxial transmission line Si, to a rectiner element 22. One end of loop 32 is connected to the outer conductor of line 3I, and the other end to its center conductor. The output terminal of rectier element 32 is by-passed to ground by a capacitor 9 which is shunted by a resistor and is coupled to one of a pair of output terminals 3d by means of capacitor 35. The other output terminal is grounded as shown.

In operation, heater II is energized, causing cathode I2 to emit electrons which are attracted in the direction of the relatively positive smoother grid I4. The flow of electrons toward cavity resonator i5 is controlled by the potential of control electrode I3, which controls .the magnitude of the electron current. The electrons pass through smoother grid i4, and then through resonator grids 36, being subjected to velocity modulation due to the action of the electric field between grids 35, and approach reflector electrode I6. Due to the negative potential of the latter, they are reversed in iiight and again enter cavity resonator I5 travelling toward the cathode, where they give energy to assist in maintaining oscillation and provide output energy. Assuming for the moment that quench-frequency oscillator 25 is rendered inoperative, velocity-modulation tube I oscillates at a frequency which depends principally upon the dimensions of cavity resonator I5 and to a minor extent upon the potentials of cavity resonator I5 and of reflector electrode IB with respect to that of cathode I2. By proper rchoice or adjustment of these variables, the frequency of oscillation may be made to correspond with that of a signal wave intercepted by antenna 29 and introduced into cavity resonator I5 by means of transmission line 28 and coupling loop 21.

If quench-frequency oscillator 25 is now made operative, the self-oscillation of tube ID will be periodically interrupted at the quench frequency, since the output of oscillator 25 is applied to control electrode I3. The rate at which the oscillatory field of resonator I5 builds up before quenching takes place is a function of the amplitude of the signal wave intercepted by antenna 251. Hence, by detecting the average strength of oscillation of tube ID, as evidenced by the oscillatory field developed in cavity resonator I5 and picked up by coupling loop 30, an output voltage which correspondents with the envelope ci the signal wave may be developed between output terminals 34.

rI'he superregenerative receiver shown in Fig. 2 of the drawing diiers from that of Fig. l in two principal respects. The receiver of Fig. 2 is of the self-quenching type, and hence requires no separate quench-frequency oscillator. Secondly, the output is derived from the change in cathode current of the velocity-modulation tube rather than by rectification or" the oscillations developed in the cavity resonator of the tube.

In the arrangement of Fig. 2, cathode I2 and control electrode I3, together with the assembly comprising smoother grid I4 and resonator I5, are connected in a. Hartley type of oscillator circuit with inductor 3l and shunt capacitor 38. Cathode l2 is coupled by means of capacitor 39 to a tap 43 on inductor 31. The lower end terminal 4I of inductor 8T is connected through grid-leak resistor 42, which is shunted by capacitor 43, to control electrode I3. The upper end terminal 2li of inductor 3T is coupled, by capacitor 45, to cavity resonator I5 and hence to smoother grid Se. Cathode I2 is maintained at a suitable direct potential, as determined by tap I8 on source I9, through choke coil 46. Likewise, the direct potential at control electrode I3 is lmaintained through choke coil 4?, `which is connected between tap 2l on source I9 and tap @D on inductor 31.

rl`he primary winding 48 of a transformer 43 is connected in series in the circuit between cathode I2 and tap I8 on source I9. Secondary winding .Til of transformer 49 'is connected between output terminals 5I.

Dipole antenna 29 is connected, by means of transmission line 22 and coupling loop 2l, to cavity resonator I5 of velocity-modulation tube IIJ. As in Fig. l, reflector electrode Ii: of tube IS is connected to tap 24 on source i9. Cavity resonator i5 of tube I 0 (and hence smoother grid 4) is connected, by means of lead 22, to the positive terminal of source i9 and at 23 to ground. Coupling loc-p 3G is not used in this arrangement.

In operation, cathode I2, control electrode I3 and the assembly ci smoother grid I4 and cavityY resonator I5 serve as the three elements of a triode which, in combination with the resonant circuit comprising inductor 3'! and capacitor 33, oscillates at a quench frequency the value of which depends upon the adjustment of capacitor When thus oscillating, it modulates the electron stream which fiows from cathode l2 through resonator grids 3G toward reilector electrode 5, the amplitude of modulation being chosen to ce suicient to render tube Ill periodically non-oscillatory.

The velocity-modulation tube operates in the same manner as described above in connection with Fig. l, to provide oscillations at the carrier frequency of the incoming signal wave within cavity resonator I5. These oscillations are periodically interrupted due to the quenching action of the above-described oscillator circuit on the electron stream.

The rate at which oscillations build up before they are quenched is a function of the amplitude of the incoming radio wave intercepted by dipole escaner antenna 29 and introduced into cavity resonator l5 by means of transmission line 23 and coupling loop 2l. The average strength of the oscillations depends on the strength of the input signal wave introduced by loop 2l. The beam current of the tube varies to some extent with the strength of oscillations in the cavity resonator. Hence, the cathode current of the tube iii varies as a function of the input-signal modulation envelope, so that an output voltage corresponding to the signal modulation is developed between output terminals 5l.

In the arrangement of Fig. 1, the quench voltage is applied between the control electrode and the cathode of the velocity-modulation tube. In the receiver of Fig. 2, the quench voltage is eifectively applied primarily between the cathode and the control electrode, with a secondary application between the cavity resonator and the cathode. t will be understood that it is within the scope of the present invention to apply the quench voltage between other electrodes or combination of electrodes of the tube. For example, the quench-voltage source could be introduced in lead 22 by closing switch 65; meanwhile, switch 535 is opened to disconnect the quench oscillator 25 from the control electrode i5 so that the quench voltage would be effectively applied between cavity resonator l5 and cathode l2. In another modification, when switch 55 is closed and switch 65 is opened, the quench voltage might be applied to reilector electrode iii in such a manner as to vary the voltage -of this electrode with respect to cathode i2 at the quench frequency. Still another arrangement would introduce the quench voltage at cathode l2 s0 that the potential of this electrode, with respect to all of the other electrodes of the tube, would change at the quench frequency; this is done by closing switch 55 and opening switch 65.

In Fig. 1 of the drawing, the output of the Velocity-modulation tube is shown as derived by rectifying the oscillations developed in cavity resonator i 5. In the arrangement of Fig. 2, the output of the receiver is developed by utilizing changes in the cathode current of the tube. It will be understood that these two diierent methods for obtaining the output of the tube may be interchanged between the systems of Figs. l and 2. In addition to the two methodsv shown in Figs. l and 2 and described above, the output of the velocity-modulation tube could also be obtained by demodulation of the quench voltage, since it has been found that the amplitude of this voltage, when the quench oscillator has relatively poor regulation, is a function of the average strength of oscillation existing in the velocitymodulatio-n tube. It will be understood that the use of the latter method for obtaining the output of the receiver in either of the arrangements of Figs. l and 2 is within the scope of the present invention.

Fig. 3 of the drawing shows an assembly which. replaces rectifier element 32 of Fig. l, and makes it possible to introduce the incoming signal waves into cavity resonator l5 by means of the same coupling loop that is used to provide an output signal. In Fig. 3, transmission line Si feeds into a crystal resonant chamber 52 which is tuned, by means of adjusting screw 55, to the carrier frequency of the incoming signal wave. Dipole antenna 29 is also coupled, through transmission line 2S, to resonant chamber 52, instead of directly to cavity resonator i5 as shown in Fig. l.

Resonant chamber 52 is shown diagrammati- 6, cally to illustrate how the transmission lines 28 and 3| are coupled to it, and how a miniature crystal detector 5d is arranged within it. Chamber 52 comprises a hollow cylindrical housing or body 55 of conductive material and having -openings in its walls to receive lines 28 and 3l. A cylindrical conductive rod 56 is positioned coaxially within housing 55, and is supported and insulated from the bottom of the housing by a dielectric .disc 5l'. With respect to the high-frequency electromagnetic eld within resonant chamber 52, rod 5B serves as a reentrant portion of a cavity resonator formed by the combination of the rod and housing 55. Discs 5S and 59, arranged in spaced relation with respect to rod 55, are attached to the inner conductors of transmission lines 28 and 5i, respectively, and serve to couple these lines to resonant chamber 52.

Detector 54 is connected between housing 55 and rod 55 as shown. An output lead 55 is also connected to rod 56, and passes through an insulating bushing 5l in the bottom of housing 55. The capacitance between the lower end of rod 5@ and the bottom of housing 55 provides a by-pass across rectifier or detector 5f! for high-frequency currents. Output lead 65 is connected to shunt resistor 33, series capacitor 35, and one of output terminals 34. The other output terminal and housing 55 of resonant chamber 52 are preferably grounded, as shown.

Such a unitary arrangement has the advantage of requiring only a single coupling loop in the tube. It also permits the operation of cavity resonator I5 at a high potential with respect to ground while housing 55 of chamber 52 and the outer conductor of transmission line 22 may be at or near ground potential, it being assumed that a single insulating bushing is provided between the outer conductor of transmission line 3l and housing 55 of chamber 52.

In one successful embodiment of the invention in accordance with Fig. 1, velocity-modulation tube l0 was a Sperry Reflex Klystron Model 417. The carrier frequency of the signal wave was approximately 3,000 megacycles per second. The sinusoidal quench voltage, developed by oscillator 25, had a frequency of 465 kilocycles per second and a value of approximately 12 volts. Source I9 had a total potential of 250 volts; and cathode I2, control electrode I3 and reflector I5 were operated, respectively, at negative voltages with respect to cavity resonator l5 of 199, 190 and 203.

In any of the above-described embodiments of the present invention, the quench frequency is chosen to permit the oscillations of the tube either to build up fully to the equilibrium value during a single oscillation period, thus providingthe logarithmic mode of operation; or to build up to a value less than the equilibrium value during each period before quenching occurs. The latter mode is referred to as the linear mode of operation.

Where the expression reiiex tube is employed, it will be understood that reference is made to an electron tube in which an electron stream is produced by a cathode, passes in a irst direction through one or more control electrodes, is reversed in its travel, and passes in the opposite direction through one or more of the same electrodes.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departure from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying to the average strength of oscillation of said tube v including a rectifier element coupled to said resonator.

2. In a superregenerative wave receiver, the combination of a reflex velocity-modulation tube having a cavity resonator therein, means for varying a control voltage applied to said tubeto render it alternately oscillatory and non-oscillatory, means for introducing an input wave into said resonator, and utilization means responsive to the average strength of oscillation of said tube including a rectier element coupled to said resonator.

3. In a superregenerative receiver, the combination of a velocity-modulation electron tube I" the reflex type having a cavity resonator therein, means for rendering said tube alternately oscillatory and non-oscillatory, means for introducing an input wave into said resonator, and utilization means comprising a detector coupled to said cavity resonator and responsive to the average strength of oscillation of said tube.

4. Superregenerative receiver apparatus comprising: an oscillator including a cathode elecn trode, a reflector electrode and a cavity resonator aligned therebetween; means coupled to one oi said electrodes for periodically quenching oscillations of said oscillator; means for exciting said resonator in response to a received wave; a detector coupled to said resonator; vand a utilization circuit coupled to said detector.

5. In a superregenerative wave receiver, the combination of a reflex velocity-modulation tube having a cavity resonator therein, means for rendering said tube alternately oscillatory and nonoscillatory, coupling means connected to said resonator for introducing an input wave thereto, and a detector in said coupling meansfor ,detecting the average strength of oscillation in said resonator.

6. The combination as defined .in claim in which said coupling means is resonantat the frequency of the cavity resonator.

'7. In a superregenerative wave receiver, the combina-tion of a klystron velocitymodulation tube havinga first cavity resonator thereimmeans for rendering said tube alternately oscillatory and non-oscillatory, a second cavity resonator coupled to said i'lrst cavity resonator, means for introducing an input Wave into said second cavity resonator, and a 4detector coupled to said second cavity resonator.

8. In a superregenerative wave receiver, zth'e combination of a Velocity-modulation `tube having at least one cavity resonator, means for rendering said tube alternately oscillatory and nonoscillatory, means for introducing an input wave into said resonator, and a detector element coupled to said resonator and directly responsive to variations in the strength of the wave therein.

9. In a superregenerative wave receiver, the combination of a reflex tube having a control electrode and a cavity resonator, said cavity resonator being adapted upon excitation to provide an alternating electric eld extending in align-'- ment with said control electrode; means including a source of varying voltage coupled to said control electrode for rendering said tube alternately oscillatory and non-oscillatory, means for introducing an input wave into said tube, and utilization means comprising a detector coupled to said cavity resonator and responsive to the average strength of oscillation of said tube;

10. The combination as dened in claim 9, in which the reflex tube is of the velocity-modulation type.

l1. In a superregenerative wave receiver, the combination of a reex velocity-modulation tube having therein a cathode, a control electrode and a cavity resonator, said cavity resonator being aligned with said control electrode and said cathode whereby electrons are adapted to flow from said cathode toward said resonator, said control electrode being adapted to regulate the electron ow toward said cavity resonator, and said cavity resonator being oscillatively coactive with electro-n flow therethrough; means including a source of varying voltage coupled to said control electrode for rendering said tube alternately oscillatory and non-oscillatory; means for introducing an input wave into said resonator; and utilization means comprising a detector coupled to said cavity resonator and responsive to the average strength of oscillation of said tube.

l2. In a superregenerative wave receiver, the combination of an electron tube, said tube having therein a cathode, a reilector electrode, and a cavity resonator aligned therebetween and adapted upon excitation to provide an alternating electric eld extending in alignment with said electrode and said cathode; means for rendering said tube alternately oscillatory and non-oscillan tory; means for introducing an input wave into said resonator; and utilization means responsive to the average strength of oscillation of said tube including a rectifier element coupled to said resonator.

13. The combination as defined in claim 12, in which the electron tube is of the velocity-modulation type.

14. The combination as defined in claim l2, in which the electron tube is of the reflex type.

l5. In a superregenerative wave receiver, the combination of a reilex velocity-modulation tube having a cavity resonator therein, said cavity resonator being adapted upon excitation to providean oscillating electric field; means for varying a control voltage` applied to said tube to render it alternately oscillatory and non-oscillatory; means for introducing an input wave into said tube; and utilization means responsive to the average strength of oscillation of said tube including a rectifier element coupled to said resonator.

i6. Supenegenerative receiver apparatus comprising: an oscillator including a cathode, a control electrode adjacent said cathode, a reilector electrode in alignment with said cathode and control electrode, and a cavity resonator between said reflector electrode and said control electrode and adapted upon excitation to provide an alternating electric eld extending in alignment with said electrodes; a source of quench frequency oscillations; means coupling said source to one of said electrodes to periodically quench oscillations in said resonator; means for exciting said resonator by a wave to be received; a detector coupled to said resonator for producing a detected signal corresponding to the average strength of oscillations in said resonator; and a utilization circuit coupled to said detector.

17. Superregenerative receiver apparatus com- REFERENCES CITED Prlsmg? means for producmg a Stream of elec' The following references are of record in the trons; cavity resonator means for velocity-modume of this patent: lating said electrons; reecting means for returning said velocity-modulated beam for further ine UNITED STATES PATENTS teractionfwith said resonator means, whereby os- Number Name Date cillations are produced in said resonator means; 1,922,195 Brown Aug. 15, 1933 means for periodically quenching said oscillations 2,129,820 Chaffee Sept. 13, 1938 at a quench frequency; means for exciting said 2,190,511 Cage Feb. 13, 1940 resonator means by a received Wave; and a de- 9 2,284,829 Ludi June 2, 1942 tector coupled to said resonator means for pro- 2,379,673 Banks July 3, 1945 ducing a signal corresponding to the average 2,406,370 Hansen Aug. 27, 1946 strength of oscillations in said resonator, said signal thereby being the modulation envelope of said received Wave.

THOMAS M. FERRILL, JR. BENJAMIN F. SPENCER. 

